1. Field Of The Invention
The present invention broadly relates to a method of producing a sintered material and more particularly, to a method of removing binder components from objects formed by injection molding of powder materials such as metal powders, ceramics and cermets.
2. Description Of The Related Art
Injection molding of a sintered product containing binder components is a well-known technique suitable for use in production of objects having complicated configurations from powder materials such as metal powders, ceramics and cermets. Since organic binders are needed in the procedure, the objects that are injection molded from such bound powder material essentially require debinding, i.e., removal of binder components, and various debinding methods have been proposed for this purpose.
For instance, Japanese Patent Publication No. 61-48563 discloses a debinding method in which an injection-molded object containing binder components is placed on a binder absorbing body and is heated so that the binder components elute in the liquid phase in the order of their melting points, i.e., such that the binder component having the lowest melting point is extracted first, while an inert gas is supplied to the injection-molded object and the binder absorbing body so as to promote evaporation of the extracted binder components in the liquid phase.
This method basically relies upon elution of the binder components in the liquid phase, so that the obtained debound object inevitably has defects in its surface contacting the binder absorption material. When the rate of elution of the binder component is small, the strength of the injection-molded object is undesirably impaired by the molten binder component remaining in the injection-molded object, often resulting in a defect such as droop.
U.S. Pat. No. 4,404,166 discloses a debinding method in which a non-saturated, chemically inert atmosphere is blown over the injection-molded object to cause the atmosphere at the surface of the object to be turbulent and unsaturated to remove a predetermined amount of binder components therefrom. Unfortunately, however, this method also fails to provide a fundamental solution to the problem of generation of defects. The generation of defects is also encountered with other known techniques.